ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Enhanced visible light photocatalytic CO₂ reduction over direct Z-scheme heterojunction Cu/P co-doped g-C₃N₄@TiO₂ photocatalyst

Mohammad Hasan Foghani, Omid Tavakoli, Mohammad Javad Parnian, and Reza Zarghami

School of Chemical Engineering, College of Engineering, University of Tehran, Tehran, Iran

E-mail: otavakoli@ut.ac.ir

Received: 29 September 2021  Accepted: 25 January 2022

Abstract:

Recently, graphitic carbon nitride (g-C₃N₄) has been considered as a promising candidate for high-performance photocatalytic CO₂ reduction. However, some drawbacks, such as high charge carriers’ recombination rate and low visible light adsorption, have limited its applications. The co-doping and constructing direct Z-scheme heterostructure have been proved to be effective approaches to enhance the photocatalytic performance of g-C₃N₄. In this work, phosphorus and copper co-doped g-C₃N₄ were successfully synthesized and then coupled with different amounts of TiO₂(P25) to obtain Cu/P co-doped g-C₃N₄/TiO₂ heterostructures. The results demonstrated that phosphorus and copper doping extended the light adsorption to the visible region, decreased the band gap energy, increased the specific surface area, and suppressed the recombination rate. Moreover, Cu/P co-doped samples exhibited a higher photocatalytic activity compared to single-doped samples. Furthermore, photoluminescence results showed that Cu/P co-doped g-C₃N₄/TiO₂ nanocomposite significantly suppressed the recombination of photogenerated charge carriers resulting in the highest CH₃OH generation yield. The optimized CH₃OH production yield reached 859 µmol g_cat⁻¹, which was about 5 and 11.6 times higher than that of g-C₃N₄ and TiO₂, respectively. In addition, the synthesized catalysts exhibited excellent stability and recyclability after a 30 h reaction for photocatalytic CO₂ reduction. Finally, the possible photocatalytic mechanism was proposed.

Keywords: Photocatalytic CO2 reduction; Cu/P co-doped g-C3N4; Methanol production; Photocatalytic activity; Direct Z-scheme heterojunction g-C3N4/TiO2

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-022-02109-z

Chemical Papers 76 (6) 3459–3469 (2022)